Posts Tagged ‘Venus

How the transit of Venus changed cinematography

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What better place to view a film about the transit of Venus than an 18th-century observatory? A once-in-a-lifetime experience, the opportunity for us to watch the planet traverse the face of the sun in June last year was the last this century and will not recur until 2117.

To mark the occasion, Modern Art Oxford and the University of Oxford commissioned Turner prizewinning artist Simon Starling to film the transit. The 35-millimetre film that Starling shot in Hawaii and Tahiti, Black Drop, is now being shown in the Radcliffe Observatory, Oxford, which was built shortly after the first global scientific effort to record the transit.

Starling’s film is being screened in the elegant Observing Room, which housed optical telescopes to investigate the night skies until the observatory closed in 1934. Conditions are chilly beneath its lofty dome in winter, even with the room’s four full-height triple windows shuttered, but it provides an evocative setting for Starling’s beguiling film, which includes images of 18th and 19th-century transits that occurred during the heyday of the observatory.

Black Drop takes its title from an optical phenomenon that occurs at a critical point during the transit of Venus, when the silhouetted planet is about to touch the sun’s edge – known as its limb – during the ingress and egress of the planet’s transit. At these points the planet appears to distort and elongate. This phenomenon foiled 18th-century observers’ attempts to collect accurate data on the exact time that the planet touched the sun’s limb, which was vital for enabling astronomers to refine their measurement of the mean Earth-sun distance – the astronomical unit. Among many disappointing failures was that of mariner James Cook and his ship’s astronomer Charles Green in 1769, who recorded very different timings for the crucial moments of contact between Venus and the sun’s limb. They did, however, publish their drawings of the black drop phenomenon in 1771.

In 1874, in order to overcome human error in collecting data during transits, the astronomer Pierre Jules César Janssen developed a “revolver photographique”, which he used to take repeated exposures of the 1874 transit of Venus. Unfortunately, the telescope to which Janssen’s chronophotographic device (combining chronometry and photography) was attached was misaligned, leaving half of Venus out of the image. But the revolver photographique had considerable impact on the subsequent development of cinema. This historical link between astronomy and cinema inspired Starling to shoot Black Drop using 35-millimetre film stock, which is being displaced by digital film-making. “Given that no one can predict what technology might be available to record the next transit in 2117, I wanted to ‘bracket’ my film historically between the introduction of Janssen’s revolver and the demise of 35-millimetre film,” he said.

Though much of Starling’s film is comprised of stills, it also includes moving images. Some of these are tracking shots of overlapping historical astronomical drawings and charts pinned onto display panels, but there is also footage of southern-hemisphere observatories and nocturnal skies, and waves washing onto Pacific beaches – signifying the historic importance of Pacific vantage points in observing transits of Venus. Starling evokes extra layers of meaning with footage of the 35-millimetre film being cut and spliced to make the final version. Shots of the editing desks from above show whirring spools of film that resemble miniature solar systems; trembling lengths of 35-millimetre film resemble the wind-blown palm trees of historic vantage points.

Black Drop is an engaging documentary, in which Starling considers astronomers’ historic interest in the transit of Venus, and their endeavours to improve the accuracy of their observations, from the viewpoint of an artist interested in the history of the development of cinema.

The Black Drop film installation runs until 24 March at the Radcliffe Observatory, Oxford, and will be recreated at Modern Art Oxford from 23 August to 8 September. Black Drop has also been published in book form

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Written by physicsgg

March 8, 2013 at 5:30 pm


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A curious cold layer in the atmosphere of Venus

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Venus terminator

Venus Express has spied a surprisingly cold region high in the planet’s atmosphere that may be frigid enough for carbon dioxide to freeze out as ice or snow.

The planet Venus is well known for its thick, carbon dioxide atmosphere and oven-hot surface, and as a result is often portrayed as Earth’s inhospitable evil twin.
But in a new analysis based on five years of observations using ESA’s Venus Express, scientists have uncovered a very chilly layer at temperatures of around –175ºC in the atmosphere 125 km above the planet’s surface.

The curious cold layer is far frostier than any part of Earth’s atmosphere, for example, despite Venus being much closer to the Sun.

The discovery was made by watching as light from the Sun filtered through the atmosphere to reveal the concentration of carbon dioxide gas molecules at various altitudes along the terminator – the dividing line between the day and night sides of the planet.

Armed with information about the concentration of carbon dioxide and combined with data on atmospheric pressure at each height, scientists could then calculate the corresponding temperatures.

“Since the temperature at some heights dips below the freezing temperature of carbon dioxide, we suspect that carbon dioxide ice might form there,” says Arnaud Mahieux of the Belgian Institute for Space Aeronomy and lead author of the paper reporting the results in the Journal of Geophysical Research.

Terminator temperature profile

Clouds of small carbon dioxide ice or snow particles should be very reflective, perhaps leading to brighter than normal sunlight layers in the atmosphere.

“However, although Venus Express indeed occasionally observes very bright regions in the Venusian atmosphere that could be explained by ice, they could also be caused by other atmospheric disturbances, so we need to be cautious,” says Dr Mahieux.

The study also found that the cold layer at the terminator is sandwiched between two comparatively warmer layers.

“The temperature profiles on the hot dayside and cool night side at altitudes above 120 km are extremely different, so at the terminator we are in a regime of transition with effects coming from both sides.

“The night side may be playing a greater role at one given altitude and the dayside might be playing a larger role at other altitudes.”

Similar temperature profiles along the terminator have been derived from other Venus Express datasets, including measurements taken during the transit of Venus earlier this year.

Models are able to predict the observed profiles, but further confirmation will be provided by examining the role played by other atmospheric species, such as carbon monoxide, nitrogen and oxygen, which are more dominant than carbon dioxide at high altitudes.

“The finding is very new and we still need to think about and understand what the implications will be,” says Håkan Svedhem, ESA’s Venus Express project scientist.

“But it is special, as we do not see a similar temperature profile along the terminator in the atmospheres of Earth or Mars, which have different chemical compositions and temperature conditions.”

Written by physicsgg

October 1, 2012 at 4:28 pm


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How to point your telescope at the Sun for the transit of Venus

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So, you have set up your scope with a solar filter (or you are using a projection system) and you ask yourself ” how the heck do I actually point the scope at the Sun”?…………
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Read also:
1. Last chance to see transit of Venus
2. Transit of Venus Event Locations
3. Watch the Venus Transit Live!
4. Transit of Venus: your last chance to see it before 2117

Written by physicsgg

June 3, 2012 at 8:18 am


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Transit of Venus

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Alan Pickup
Britain is poorly placed for views of the astronomical highlight of 2012, but the situation is not hopeless. To see the whole of the transit of Venus across the Sun’s disc on June 5-6, though, it is not too late to travel eastwards, perhaps to areas around the W Pacific. If we are quick enough, we could even take in the annular eclipse of the Sun which begins over E China and Hong Kong next Monday morning, local time, and ends (after crossing the date line) on Sunday evening over the SW USA.
Venus is an outstanding evening star to the N of W at nightfall tonight, its altitude at sunset falling to 15° by the 22nd when it stands above the slimmest of young moons. We probably lose it in the twilight a week later and after another week its inky black disc crosses the N part of the Sun as shown by our diagram.

Seen from the direction of the Earth’s centre, Venus first touches the Sun’s NE limb at 23:10 BST on 5 June, is farthest on to the disc at 02:30 on the 6th and finally leaves the WNW limb at 05:49. In fact, these times vary by up to 6 minutes depending on our location on the Earth; as seen from much of Britain, for example, Venus does not disappear from the Sun until 05:55.

Britain’s problem is that most of the transit occurs before the Sun rises above our NE horizon. For example, sunrise for London, Cardiff and Belfast occurs at 04:45, 04:58 and 04:51 respectively. Scotland, particularly N and E Scotland, fares better, with sunrise for Edinburgh coming at 04:30. As the transit ends, the Sun stands 8° high as seen from London and 9° high for Edinburgh.

Even though the Sun is low in the sky, serious eye damage is likely if we look directly at it through a telescope or binoculars. Instead, project the Sun’s image through the eyepiece on to a white card or obtain an approved solar filter to block the Sun’s heat and intense light before it enters the optics.

The fact that the time of a transit varies worldwide was of major interest during the 18th and 19th centuries, for exact timings could be used to triangulate the distance to Venus, and hence the scale of our solar system. Expeditions to far-off locations to secure observations included the first voyage by James Cook who timed the transit of 1769 from Tahiti.

Part of the romance of such events is their rarity; there have been only three transits since Cook’s venture, those of 1874, 1882 and 2004. Britain, at least those parts without too much cloud, witnessed the whole of the 2004 event but we need to wait until 2247 for an equally-favourable one. Before then there are transits in 2117, which occurs in the middle of a winter’s night for Britain, and 2125 when the Sun sets at about mid-transit….
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Written by physicsgg

May 13, 2012 at 11:00 pm


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The transit of Venus across the Sun

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It’s a twice in a lifetime moment

On 6 June, an event that takes place only four times every two centuries will enthral the world’s astronomers, as it has ever since the 1600s – but now it can provide priceless data in the hunt for habitable planets in deep space

The tiny black disc of Venus edges across the Sun during the last transit, in 2004. Photograph: Murdo MacLeod for the Observer

By Robin McKie
A tiny speck will appear on one side of the Sun in a few weeks and slowly traverse the solar disc for a few hours. The movement of that little black dot may seem insignificant. But it is one of the rarest sights in astronomy, an event known as a transit of Venus. Miss this one and you will have to wait until 2117 for the next.

Earth’s closest planetary neighbour, which is currently in close and spectacular alignment with Jupiter in the night sky, will make its passage across the Sun’s disc on 6 June and can expect to make scientific headlines – for astronomers hope studies of the transit will provide them with key data for studying worlds that orbit distant stars.

“This transit is special because it is the last time in our lifetimes that we will have an opportunity to collect data for a planet as well characterised as Venus,” said David Crisp of Nasa’s Jet Propulsion Laboratory in Pasadena, California. “We will have to make the most of it.”

Venus, for all its glittering beauty in the night sky and its association with the Roman goddess of love, is a deeply unpleasant world. It has a surface temperature of 460C, its dense atmosphere of carbon dioxide has incinerated or crushed all robot spacecraft that have landed on it and its surface is shrouded by thick clouds of sulphuric acid. Once thought to be a sister world to Earth, because of their similar sizes and orbits round the Sun, Venus is more like a vision of hell…..
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Written by physicsgg

March 25, 2012 at 4:27 pm


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Venus and Jupiter: how to spot them

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The two planets will appear side-by-side in western skies for the next two evenings – offering a dazzling spectacle. So where and how can you best see them?

A crescent moon hangs in the sky above Venus (on the left) and Jupiter in the evening sky in 2008. Photograph: Jamie Cooper/Getty Images

After the moon, they are the two brightest objects in the night sky, and for the next few evenings they will appear side-by-side in western skies in a dazzling heavenly spectacle.

Though Jupiter is seven times farther from Earth than Venus, the planets’ orbits bring them into close approach on Tuesday evening, when they will appear only three degrees, or a few finger-widths, apart…. Read the rest of this entry »

Written by physicsgg

March 13, 2012 at 4:24 pm


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Is this life on Venus?

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Russian scientist claims to have seen ‘scorpion’ in probe photographs

  • Scientist sees shapes in 1982 Soviet probe pictures
  • No previous records of life on the hottest planet in solar system

A Russian scientist claims to have discovered life on Venus after analysing photographs taken by a Soviet probe that landed on the planet’s surface 30 years ago.
The pictures – taken by the probe Venus-13 in 1982 – have been re-examined by Leonid Ksanfomaliti of the Space Research Institute at Russia’s Academy of Sciences.
Ksanfomaliti said the images showed a scorpion-shaped body, a disc and a ‘black flap,’ which apparently moved as the probe’s camera records the scene.

New life? Russian scientist Leonid Ksanfomaliti, claims this image, taken from a probe that landed on Venus in 1982, shows a scorpion-shaped life formA

They all ’emerge, fluctuate and disappear,’ explained Ksanfomaliti, writing in the Russian journal Solar System Research magazine, according to reports.
‘What if we forget about the current theories about the non-existence of life on Venus, let’s boldly suggest that the objects’ morphological features would allow us to say that they are living,’ he added.
The Russian scientist is the author of several space publications including the book Mercury.
There are no records of life on Venus, which has a surface temperature of 464 degrees Celsius.
‘Similar in structure and size to Earth, Venus’ thick, toxic atmosphere traps heat in a runaway “greenhouse effect,’ says Nasa.
Scientists have not ruled out the possibility of life having once existed on Venus – but most research has focused on whether there were oceans, and possibly life, in the distant past, before the ‘greenhouse effect’ created the scorching temperatures that exist on the surface today.

Venus, as mapped by Nasa's Magellan probe: The probe used radar to map the planet's surface before plunging into Venus's hellishly hot atmosphere

‘Current theories suggest that Venus and the Earth may have started out alike. There might have been a lot of water on Venus and there might have been a lot of carbon dioxide on Earth,’ Professor Andrew Ingersoll of Caltech said in a paper published in Astrobiology in 2004.
Since the Russian probe visited the planet, Nasa probes have created much more detailed pictures of the surface – in which no living beings appear.

This composite picture of Venus was created from Nasa's radar investigations including Magellan's 1990-1994 mission. The planet's surface is hot enough to melt lead, heated by a runaway 'greenhouse effect'

Nasa’s Magellan spacecraft, named after the sixteenth-century Portuguese explorer whose expedition first circumnavigated the Earth, was launched May 4, 1989, and arrived at Venus on August 10, 1990.
During the first eight-month mapping cycle around Venus, Magellan collected radar images of 84 percent of the planet’s surface, with resolution 10 times better than that of the earlier Soviet Venera missions.
‘During the extended mission, two further mapping cycles from May 15, 1991 to September 14, 1992 brought mapping coverage to 98% of the planet, with a resolution of approximately 100m,’ says Nasa………….
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Read also: Leonid Ksanfomaliti: 1982 Russian Probe Photos Proof of Aliens on Venus?

Written by physicsgg

January 23, 2012 at 1:39 pm


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Venus Weather Not Boring After All….

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….NASA/International Study Shows

Ultraviolet image of Venus' clouds as seen by the Pioneer Venus Orbiter (Feb. 26, 1979). Credit: NASA

At first glance, a weather forecaster for Venus would have either a really easy or a really boring job, depending on your point of view. The climate on Venus is widely known to be unpleasant – at the surface, the planet roasts at more than 800 degrees Fahrenheit under a suffocating blanket of sulfuric acid clouds and a crushing atmosphere more than 90 times the pressure of Earth’s. Intrepid future explorers should abandon any hope for better days, however, because it won’t change much.
“Any variability in the weather on Venus is noteworthy, because the planet has so many features to keep atmospheric conditions the same,” says Dr. Tim Livengood, a researcher with the National Center for Earth and Space Science Education, Capitol Heights, Md., and now with the University of Maryland, College Park, Md.
“Earth has seasons because its rotation axis is tilted by about 23 degrees, which changes the intensity of sunlight and the length of the day in each hemisphere throughout the year. However, Venus has been tilted so much, it’s almost completely upside down, leaving it with a net tilt of less than three degrees from the sun, so the seasonal effect is negligible,” explains Livengood, who is stationed at NASA’s Goddard Space Flight Center in Greenbelt, Md. “Also, its orbit is even more circular than Earth’s, which prevents it from getting significantly hotter or cooler by moving closer to or further away from the sun. And while you might expect things to cool down at night — especially since Venus rotates so slowly that its night lasts almost two Earth months — the thick atmosphere and sulfuric acid clouds act like a blanket while winds move heat around, keeping temperatures pretty even. Finally, almost all the planet’s water has escaped to space, so you don’t get any storms or precipitation like on Earth where water evaporates and condenses as clouds.”

A set of images of the Venus south polar vortex in infrared light (at 3.8 microns) acquired by the Visible and Infrared Thermal Imaging Spectrometer instrument on ESA's Venus Express spacecraft. The images show the temperature of the cloud tops at about 65 km (40.4 miles) altitude. A darker region corresponds to higher temperature and thus lower altitude. The center of the vortex, at a temperature of about 250K (around minus 9.7 degrees Fahrenheit), is the deepest zone, exhibiting the highest temperature. Credit: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

However, higher up, the weather gets more interesting, according to a new study of old data by NASA and international scientists. The team detected strange things going on in data from telescopic observations of Venus in infrared light at about 68 miles (110 kilometers) above the planet’s surface, in cold, clear air above the acid clouds, in two layers called the mesosphere and the thermosphere….. Read the rest of this entry »

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September 27, 2011 at 7:15 pm


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